Cooling apparatus



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Faiented Bec., i9, 1950 CGOLING APPARATUS Carl L. Ipsen. Schenectady,and Norman B. Jones, Ballston Lake, N. Y., assignors to General ElectricCompany, a corporation of New York Application March z, 1949, serial No.79,256

(ci. 26o- 3) 1 claim. l

Our invention relates to cooling apparatus for hot metals and moreparticularly to apparatus of the type adaptable for location at the exitof a continuous strip annealing furnace to provide controlled cooling ofthe continuous metal strip.

The primary object of our invention is the provision of a simple andreadily controlled cooling apparatus of this character which providesuniiorm cooling of hot strip material.

Another object of the invention is. the pro-A vision oi' a coolingapparatus for location at the outlet of a continuous strip annealingfurnace which is economical to construct and economical to maintain andoperate.

In the annealing of continuous strip material auch as steel strip, forexample, it is necessary to control the rate of cooling of the stripafter it emerges from the furnace in order to provide the strip materialwith the desired physical properties. To accomplish such cooling it'iscustomary to pass the hot strip through one or more enclosed coolingchambers immediately after it leaves the furnace. In these coolingchambers the strip material is cooled usually by radiation from the hotstrip to the outer enclosures of the cooling chambers or to water-filledcooling coils within the chambers. In some cases, the strip material iscooled b v a combination of radiation and convection, with fans beingprovided for internal circulation of the atmosphere in the coolingchambers. The method of removing at least a part of the heat externallyis also known, in which case the atmosphere in the coollng chambers isremoved. passed through external coolers and then returned to thecooling chambers.

.All oi the foregoing methods of removing heat from the strip materialhave disadvantages. In the iirst two cases of cooling by radiation onlyor by a combination of radiation and convection, the principaldisadvantage is the large size of the cooling apparatus which isrequired to properly cool rapidly moving strip material. A furtherdisadvantage of these two methods is the difiiculty of accuratelycontrolling the cooling, particularly under abnormal conditions. Thechief disadvantage of the third or atmosphere removal method of coolingis the possibility of warping the hot strip material by bringing theincoming cold atmosphere in contact with the strip, while a furtherdisadvantage of this method is the high cost of the external atmospherehandling equipment.

It is an object of our invention to provide a cooling apparatus for hotstrip material which is relatively small in size in comparison withequipments previously used for the same purpose.

A still further object of the invention is the provision of a coolingapparatus which provides accurately controllable cooling in order tominimize the possibility of strip warpage.

Additional objects of our invention, together with the features andadvantages thereof will become apparent from the reading of thesubsequent detailed description in conjunction with the accompanyingdrawing.

In' carrying out our invention in one form, we provide a coolingapparatus for continuous steel strip which has six vertical chambersarranged in a continuous row. Alternate chambers are interconnected atthe top and at the bottom and each interconnecting space between twochambers is provided with a roller. The steel strip enters the apparatusthrough an inlet opening in one endmost chamber, passes longitudinallythrough successive cooling chambers as it is supported vertically ineach chamber by said rollers, and leaves the apparatus through an outletopening in the other endmost chamber. The cooling apparatus is providedwith an artificial non-oxidizing atmosphere which is circulated throughsuccessive cooling chambers in a direction opposite to the movement ofthe steel strip material through the chambers. The atmosphere is removedfrom thechamber containing the steel inlet opening and is reintroducedinto the chamber containing the steel outlet opening to provide thiscirculation. At a point near the inlet opening for the steel strip acontrollable portion of the atmosphere is extracted and after beingcooled is mixed again with the main portion of the atmosphere before thelatter is reintroduced into the outlet chamber. the atmosphere iscontinuously circulated through the apparatus in a direction opposite tothe movement of the steel strip therethrough, with a portion of theatmosphere being cooled during each cycle.

For a more complete understanding of our invention, reference should behad to the accompanying drawing, Fig. 1 of which is a sectional view ofa cooling apparatus embodying our invention; Fig. 2 is a partial endview in outline of the lower portion of the apparatus illustrated inFig. l; and Fig. 3 is a side outline view of the same portion of theapparatus which is shown in Fig. 2.

Referring to Fig. 1 of the drawing, a cooling apparatus embodying ourinvention is designated Thus, all

generally by the numeral I. The cooling apparatus I has an outerenclosure on all tour sides and top and bottom composed of an outerlayer 2 of metal and an inner layer 3 o! heat insulating material. Theupper part of enclosure 2, 3 is divided into six vertical coolingchambers or passages consisting of end chambers 4 and 5 and fourintermediate chambers 6. The enclosure 2, 3 is supported laterally byvertical structural steel members II and horizontal cross members I2,which are best seen in Fig. 2.

The vertical cooling chambers `are interconnected alternately at the topand at the bottom. In cach interconnecting opening and locatedsubstantially half in each chamber is a transverse roller 1. End chamber4 has an entrance roller 3 at the bottom thereof, while end chamber 5has an exit roller 9 positioned in an outward extension I II ofenclosure 2, 3.

Positioned immediately adjacent to the` entrance to cooling apparatus Iin a typical apparatus embodying our invention is a high temperatureelectric annealing furnace I3. Furnace I3 may, for example, be of thetype disclosed in copending application Serial No. 79,252 of Albert N.Otis, now Patent No. 2,491,828. which is assigned to the assignee of thepresent invention and which was led concurrently herewith. This furnacecomprises a plurality of vertically disposed heating chambers I4 withelectric heating velements I5 positioned on the side walls of chambersI4 to provide a source of heat. A continuous strip I6 of steel, which isto be annealed, is passed vertically through the heating chambers I4 offurnace I3 by means of rollers I1 located at the top and bottom of eachheating chamber.

After the strip material I6 leaves the annealing furnace, it enterscooling apparatus I through an entrance opening I8, after which itpasses beneath roller 8. From roller 8 it passes consecutively aroundupper and lower rollers 'I until it reaches exit roller 9 followingwhich it leaves the cooling apparatus through an outlet opening I9.

From opening I9, the strip I6 passes into a conduit which takes it tothe next process (not shown) in the treatment of steel strip.

Cooling apparatus I is constructed to operate with an artificialnon-oxidizing atmosphere which may, for example, be of hydrogen or amixture of hydrogen and nitrogen. A suillcient quantity oi.' the gaswhich is used to provide the artificial atmosphere is continuously putinto the cooling chambers 4 and 5 through pipes 2| to maintain thepressure in apparatus I above the surrounding atmospheric pressure. Theatmosphere is circulated through the end cooling chambers 4, 5 andintermediate cooling chamber 5 in a direction opposite to the movementof steel strip IB through these chambers. This circulation is providedby a blower 22 which may be driven by an electric motor 23 through abelt drive mechanism composed of driving pulley 4I, belt 24 and drivenpulley 42. Blower 22 forces the atmosphere upward in chamber 5 in thedirection indicated by the arrows in Fig. l, after which the atmospheremoves alternately downward and upward through intermediate chambers land ilnally downward through chamber 4.

A From chamber 4 the atmosphere is drawn by blower 22 through an opening25 in the bottom of chamber 4 which may be equipped with a ilap valve 26into chamber 21 which occupies all of the lower portion of the coolingapparatus enclosure.. From chamber 21 the atmosphere is again picked upby blower 22 and recirculated up through chamber 5 and thence throughthe intermediate chambers Ii and end chamber 4 back to bottom chamber21. On the side walls of interconnecting passage or chamber 21 arelocated a plurality of heating elements 28 which may be of theelectrical resistance type, with the heating elements being surroundedby vertical and horizontal projections 29 of heat refractory materialfor mechanical protection.

On each side of entrance chamber 4 is located an opening 30 which isconnected by means of a duct 3| to an atmosphere cooler 32. Cooler 32may be of the shell and tube type with the cooling water enteringthrough a pipe connection 33 and leaving the cooler through a connection34. A duct 35 .connects the atmosphere outlet 'connection of cooler 32to a blower 36 which may be driven by an electric motor 31 through abelt drive mechanism composed of a driving pulley 43, a belt 38, and adriven pulley 44. The atmosphere outlet of the blower 36 is connected toan opening 39 in chamber 5 by means of a variable opening valve 4II.

In the operation of cooling apparatus I, steel strip I6 enters theapparatus through opening I8. The strip I6 passes ilrst around roller 8.then alternately around upper and lower rollers 1, thence around rollers and out of the cooling apparatus through opening i9. The atmosphere iscirculated upward through chamber 5, alternately downward and upwardthrough chambers 6 and downward through chamber 4 1n the oppositedirection to the motion of steel strip I6. As the steel strip and theatmosphere move counter to each other, the former is cooled and thelatter is heated. The point of highest atmosphere temperature in thecooling apparatus, for usual operation, is at the bottom of chamber 4and the point of lowest atmosphere temperature is in chamber 5, aboveatmosphere inlet 39, with an approximately uniform atmospheretemperature gradient between these two points along the path ofatmosphere flow through the series of cooling chambers. Thus, thetemperature of the steel strip is reduced gradually and at approximatelya uniform rate as it moves from inlet opening I8 to outlet opening I9.

In order to reduce the temperature of the atmosphere which is drawn fromthe bottom of chamber 4 by blower 22 and reintroduced into chamber 5, aportion of the hot atmosphere is extracted through openings 30 inchamber 4. This portion of the atmosphere is drawn through coolers 32 byblowers 36, after which it is injected back into the atmospherecirculating system through openings 39 in chamber 5. It will be notedthat openings 39 are well below the point at which the recirculatedatmosphere rst comes in contact with the steel strip I5. This permitsthe cooled atmosphere from openings 39 to be thoroughly mixed with thehotter portion of tha. atmosphere being blown upward through chamber 5by blower 22. Thus, the atmosphere is at a uniform temperature when itcomes in contact with strip I6 and the possibility that the steel stripI6 may be warped by the cooler atmosphere is minimized.

Another advantage of our invention is that a relatively small volume ofatmosphere is circulated externaliy through the shell and tube typecoolers, whereas a relatively high volume is recirculated through thestrip cooling chambers by the internal fan 22. This reduces both thesize and cost of the equipment required for handling atmosphereexternally to the main cooler enclosure 2, 3. At the same time, theadvantages of convection cooling are retained by cooling a portion ofthe furnace atmosphere and mixing the cooled portion with the balance ofthe atmosphere before it is recirculated through the furnace. A largevolume of circulating atmosphere is necessary for satisfactoryconvection cooling, and a large volume is achieved by our inventionwithout the necessity of removing all the atmosphere from the coolingapparatus and reintroducing it again.

The heating units 28, which are located in lower chamber 21, are for thepurpose of adding heat to the atmosphere under abnormal conditions ofoperation. Such a condition may occur, for example, when it is necessaryto move the strip i6 through the cooling apparatus at lower than thenormal speed. In such a case, it may be necessary to raise thetemperature of the circulating atmosphere in order to prevent the stripfrom cooling too rapidly. In this event, valves 40 are closed to stopthe operation of coolers 32 and heating units 28 are energized from asource of electrical current to add heat to the atmosphere. Automaticmeans (not shown) are provided for controlling valves 40 and heatingunits 28 responsively to the temperature of the strip in chamber 5.

Although heating units 28 are located in chamber 21 in this embodimentof our invention, they may be located instead in the lower portion ofchamber if desired, with equal eilect.

This method of adding heat to the atmosphere when necessary, togetherwith variable opening valves 40 which make it possible to regulate theportion of the atmosphere which is cooled, makes possible the accuratecontrol of the temperature oi' strip material I6 over a wide range ofoperating conditions. Furthermore, the counterflow arrangement of ourinvention which makes it possible to utilize heat removed from the stripbeing cooled to retard the cooling rate of another portion of the samestrip, allows the use of fewer heating units 28 than would be the caseif it were necessary to provide in this way all the heat required toaccurately control the strip temperature under abnormal conditions.

While we have illustrated and described one preferred embodiment of ourinvention, many modications thereof will occur to those skilled in theart and, therefore, it should be understood that we intend to cover bythe appended claim anv such modifications as fall within the true spiritand scope of our invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

Apparatus for coolingr continuously moving strip material at apredetermined rate, said apsupporting said strip material in saidchambers and providing for the passage of said material longitudinallythrough `consecutive interconnected chambers, an entrance opening forsaid strip material in one endmost chamber, an exit opening for saidstrip material in the other endmost chamber, means including anatmosphere outlet opening in the strip entrance chamber, an atmosphereinlet opening in the strip exit chamber. an interconnecting passagebetween said atmosphere outlet and inlet openings, and a blower, forrecirculating said atmosphere through consecutive interconnectedchambers in a direction opposite to the movement of said strip 'materialtherethrough, whereby a part of the heat removed by convection from saidstrip material in the portion of the apparatus nearer the strip entranceis returned to the strip material in the portion nearer the strip exit,selective hgating means for adding heat to said atmosphere after it hasleft the cooling chambers and before it is returned for recirculationthrough them, and selective means for extracting a variable portion ofsaid atmosphere from the circulating system, cooling said portion, andreturning said portion to said system to aiect the temperature of all ofthe atmosphere, said last-named means comprising an extraction openingin said strip entrance chamber, a controllable opening in said stripexit chamber, an linterconnecting duct between said extraction openingand said controllable opening, an atmosphere cooler, and a secondblower, whereby the temperature of said strip material is reducedsubstantially uniformly and at a predetermined rate irrespective of thespeed of movement of the strip material through the cooling apparatus.

CARL L. IPSEN. NORMAN B. JONES.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,023,285 Otis Dec. 3, 19352,199,472 Wean May 7, 1940 2,232,391 Keller Feb. 18, 1941 2,345,181Cooper et al. Mar. 28, 1944 2,441,500 Miess May 11, 1948

